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Removal of Unit from Common Venting System
In the event that an existing furnace is removed from a
venting system commonly run with separate gas ap-
pliances, the venting system is likely to be too large to
properly vent the remaining attached appliances. The fol-
lowing test should be conducted while each appliance is in
operation and the other appliances not in operation remain
connected to the common venting system. If the venting
system has been installed improperly, the system must be
corrected as outlined in the previous section.
1. Seal any unused openings in the common venting sys-
tem.
2. Visually inspect the venting system for proper size and
horizontal pitch and determine there is no blockage or
restriction, leakage, corrosion or other deficiencies
which could cause an unsafe condition.
3. If possible, close all building doors and windows and
all doors between the space in which the appliances
remaining connected to the common venting system
are located and other spaces of the building. Turn on
clothes dryers and any appliances not connected to
the common venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts, so
they will operate at maximum speed. Do not operate
a summer exhaust fan. Close fireplace dampers.
4. Following the lighting instruction, place the appliance
being inspected in operation. Adjust thermostat so ap-
pliance will operate continuously.
5. Test for spillage using a draft gauge.
6. After it has been determined that each appliance re-
maining connected to the common venting system
properly vents when tested as outlined above, return
doors, windows, exhaust fans, fireplace dampers and
any other gas burning appliance to their previous con-
dition of use.
7. If improper venting is observed during any of the
above tests, the common venting system must be cor-
rected.
Horizontal Venting
The OHR23 is approved for horizontal venting with the fol-
lowing mechanical vent systems:
Tjernlund (sideshot) #SS1C (Cat. #35E08) or Field Con-
trols #SWG−5 (Cat. #35P08) with the CK−61 (Cat. #18N28)
control kit. Refer to the manufacturers’ installation instruc-
tions for proper installation procedures and service parts
information.
Do not use the same vent with any other appliance when
using a sidewall vent system.
Maximum permissible vent length is 70 equivalent feet.
Minimum length is 15 equivalent feet. Calculate the equiv-
alent vent pipe footage from the furnace to the mechanical
vent system (Tjernlund or Field Controls) by adding the
straight vent pipe length and the equivalent elbow lengths
together.
Use the barometric draft control in the horizontal (sidewall)
venting system. Locate the barometric draft control within
18 inches of the furnace flue outlet. See figure 14 for baro-
metric draft control location.
Horizontal Venting / Downflow Application
BAROMETRIC
CONTROL*
HORIZONTAL
VENTING CON-
TROL
Figure 14
*BAROMETRIC CONTROL MUST BE INSTALLED IN THE HORIZONTAL VENTING
SYSTEM AND LOCATED WITHIN 18" OF FLUE OUTLET OF FURNACE.
Horizontal Venting / Horizontal Application
CONTROL FOR
HORIZONTAL
VENTING
BAROMETRIC
CONTROL*
Flue Connections
IMPORTANT
When flue pipe is installed at less than minimum
clearance listed in tables 2 and 3, radiation shields
must be installed. See figure 15.
Use 24 gauge or heavier galvanized smoke pipe and fit-
tings to connect furnace to vent. Maintain rise of at least
one inch per foot. Connect flue pipe to chimney using the
least number of elbows and angles possible. Flue pipe or
vent connector must be inserted into but not beyond the
outside wall of the chimney flue. No reduction in diame-
ter of flue pipe is acceptable. It is best to have flue pipe as
short and direct as possible.
Where two or more appliances vent into a common flue,
the area of the common flue should be at least equal to
the area of the largest flue or vent connector, plus 50% of
the area of any additional flues or vent connectors.
Install barometric draft control (provided) and flue pipe
according to instructions packed with control.
1. Install draft control, provided, and flue pipe according
to instructions packed with control.
2. Connect flue outlet to chimney using at least 24 gauge
vent pipe and fittings, the same size as the flue outlet.
3. Use the least number of elbows and angles possible.
Slope flue pipe toward chimney approximately 1/4" for
